Bests & Worsts Reviews from Amazon

I hate math and so do you, but with a little calculation and a couple hours of research, you can do a great job picking an air filter and weeding out marketing nonsense. First, the government CADR rating always has three levels that represent different *size* particles. They name them Dust, Pollen, and Smoke to represent big, medium, and tiny particles (of any kind!). The smallest, "Smoke", represent those tiny HEPA particles such as many allergens. Therefore, if you are shopping for a HEPA filter, you should only focus on the Smoke CADR results. The second thing to know is that the government believes people with bad allergies need air exchanged in the room 4-5x per hour, and non-allergy sufferers 2x per hour, to make it worth it. Anything lower and the particles may fall to the ground on their own, or you may just not feel a difference. (Once they fall, I recommend a vacuum with a HEPA filter such as Miele). Their calculation includes an open door to another room, and results get much better with a closed door, but you still need fresh air so you don’t get overwhelmed with carbon dioxide imbalance so keep your door open a little. Finally, CADR is calculated on max fan speed. NOBODY uses their air filter on max, lets face it!! In fact, my goal is to run my air filter on low because I know I can totally live with it no problem. So now begin your shopping. Find the brands you trust or heard good word of mouth, and visit their websites and download their manuals. There you will usually find the CADR listed and the CFM output at different fan speeds. If only one CFM is listed it is for max speed, so you can look at the power use of the fan and calculate the CFM of different speeds proportionately. For example if the low power setting is 1/3 of the max, you are probably getting 1/3 of the advertised CFM on the low fan speed. Take the CFM output from Smoke listed in the manual and divide it into the cubic feet of your room. The blue air Classic 205 says low fan speed outputs 75 CFM for smoke sized particles. (Again, smoke size are the HEPA particles that matter). My bedroom is 12 x 12 x 8’, so I divide 75 CFM (low output) into (12*12*8) 1152, and I get about 15. This means it takes 15 minutes to clean the air. Per hour, I will therefore get 4 air exchanges. Perfect! I never have to go higher than low fan speed. Using this method, I discovered the Rabbit Air is totally useless on almost all settings. Of course people will say the low setting is quiet - its not getting the job done whatsoever. It needed a room so small nobody would live in. So make sure to use this formula and guesstimate or calculate the room you will use it in and the speed you will use. Don’t let them trick you! You may need to buy a larger air filter if you want the lower speeds to be practical. Some brands are pure marketing, and are useless on low speeds. Finally, the filter replacement usually follows the same rule of max fan speed and 24/7 use. Blue Air says I need to replace it in 6 months. Since I run mine 12 hours per day (overnight) on low, I can calculate the proportion. 75 CFM is 35% of the highest setting 220 CFM, so running it 24/7 would mean I don’t change the filter for about 17 months. Since I will run it half the day, I don’t change it for 35 months! Sounds right; if you google for when to change HEPA filters it says they “typically” need to be changed every 3-5 years. Boom. Saved myself a fortune. So far, the Blue Air is working great and has a smooth quiet sound. I will give it 5 stars if nothing goes wrong over time. Hopefully this helps you. Do your own due diligence and good luck -- Update : After a year it is working the same as when I bought it so I moved to 5 stars. The app sometimes causes some trouble. I do not like companies that make you connect to the internet because they scrape your data. I believe the EULA says they upload your data to their servers which likely means it gets in giant correlative databases and sell it to unseen third parties, which is the basic business plan of Silicon Valley. For example, maybe people who live in Los Angeles who have their air filter turn on at bedtime who also recently bought fancy cheese are more likely to own a Tesla. This is the how Google and Facebook work and anyone who scrapes your data. I cannot be sure Blue Air does its well known companies are dying to get into your house (Google purchased Nest for this reason). I also wish I bought the smokestop filter because many times toxic smells came up such as weed killer accidentally used outside etc.